vault backup: 2022-08-04 11:16:03

content/notes/08-intro-to-c.md

@@ -9,9 +9,55 @@ tags:
 Developed 1972 for Unix
 
 - widely used
+	- compilers esxist for most OSs and architectiures
 - diverse use
+	- OSs, device drivers, protocol stacks
+	- less so for application software
 - low level
-- not Object Or
+	- language features map to CPU features 
+- not Object Oriented
+	- no classes etc
 
 > “C is an imperative procedural language supporting structured programming, lexical variable scope, and recursion, with a static type system. It was designed to be compiled to provide low-level access to memory and language constructs that map efficiently to machine instructions, all with minimal runtime support. Despite its low-level capabilities, the language was designed to encourage cross-platform programming. A standards-compliant C program written with portability in mind can be compiled for a wide variety of computer platforms and operating systems with few changes to its source code.” - wikipedia
 
+```
+#include <stdio.h>
+
+int main(int argc, const char *argv[])
+{
+	puts("Hello World");
+	return 0;
+}
+```
+
+# \#include
+java uses .class files, C uses .c and .h
+- .c for implementation
+- .h for extern declarations (similar to `public`)
+
+java uses `import`, C uses `#include`
+
+```
+#include <stdio.h>
+#include "myfile.h"
+```
+
+- `#include` literally includes the file with the given name right there into the file eing compiled
+- in `hello_world.c` we include `stdio.h` so we can call `puts()`
+
+# Routines
+```
+int main(int argc, const char *argv[])
+{
+
+}
+```
+
+routines can be scoped to just the source code file
+- `statis int eleven(void`
+
+routines must be declared bfore being used
+- `extern int eleven(void)`
+
+# If statements
+